KR20110088545A - Method for producing an optoelectronic semiconductor chip and optoelectronic semiconductor chip - Google Patents

Abstract

A method of manufacturing an optoelectronic semiconductor chip is provided, the method comprising the steps of: A) forming a semiconductor layer sequence 200 having at least one doped functional layer 7 wherein the functional layer comprises at least one dopant and at least one A conjugated complex containing a co-dopant, wherein one selected from the dopant and the co-dopant is an electron acceptor and the other is an electron donor), B) the energy (14, 15) input using Activating the dopant by bond complex breakdown, wherein the codopant remains at least partially in the semiconductor layer sequence 200 and at least some does not form a bond complex with the dopant. Also provided is an optoelectronic semiconductor chip.

Description

Method for manufacturing optoelectronic semiconductor chip and optoelectronic semiconductor chip {METHOD FOR PRODUCING AN OPTOELECTRONIC SEMICONDUCTOR CHIP AND OPTOELECTRONIC SEMICONDUCTOR CHIP}

This patent application claims the priority of German patent application 10 2008 056371.4, the disclosure content of which is incorporated herein by reference.

A method for manufacturing an optoelectronic semiconductor chip and an optoelectronic semiconductor chip are provided.

In addition to the inherent doping of many materials, especially in bandwidth semiconductors, co-doping with a second material is required when fabricating a semiconductor layer containing expensive crystals while being highly doped in a semiconductor chip. For example, electron acceptor materials are inserted when high p-type doping is desired to increase the charge carrier concentration, ie increase the hole concentration. At the same time, in order to counteract the degradation of crystal quality, additionally an electron donor material is inserted as a co-dopant, through which the electrical neutrality of the crystal is at least partially regenerated. Co-doping may also be unexpectedly required by the method of manufacture. As described above, in the above-described example, in the case of p-doped and n-doped layers, co-doping causes very low p-type doping, or intrinsic charge carrier concentration, or n-type doping. For the high hole concentrations for the desired high p-type conductivity in the examples mentioned, the compensating effect of the codopant must be offset again, which is called activation of electrical conductivity, activation of p-type conductivity or activation of dopant in the examples provided above. .

Electrical activation of such co-doped semiconductor material is generally accomplished by activation in the form of purely annealing steps with heat. For this purpose, the codopant is more easily volatilized than the dopant and the codopant must be able to be released from the doped semiconductor layer to a certain extent or completely, ie, by 0.001% to 100%, by a thermal annealing step. This method is required for p-type activation of, for example, GaN-based light emitting diodes (LEDs). For this activation, for example, there is a method established based in particular on the so-called RTP- ("rapid thermal processing"-) process under a specific atmosphere. Conventional activation processes are in the form of an RTP process at high temperatures of 700 to 1000 ° C. in the wafer bond or relatively longer times at lower temperatures of 500 to 600 ° C. in the wafer bond in a tube furnace. While other gas mixtures are made.

However, known methods do not play a sufficient role in preventing the co-dopant from diffusing from the doped semiconductor material for any reason, as is the case for example with so-called buried p-type doped layers. The degree of activation that can be achieved in the co-doped p-type layers that are exposed, i.e. near the crystal surface and using the conventional method described above, and embedded below one or more layers, in particular n-type doped layers There is a significant difference in the degree of activation that can be achieved in p-type doped layers. In the latter case, using only known methods of activation can only be activated to a slight extent or not at all. This significantly increases the drive voltage measurable in devices such as LEDs, for example.

An object of at least one embodiment is to provide a method of manufacturing an optoelectronic semiconductor chip comprising at least one doped functional layer. Another object of at least one embodiment is to provide an optoelectronic semiconductor chip.

This problem is solved by the method and the object of the independent claims. Advantageous embodiments and developments of the method and the object are characterized by the dependent claims, which also arise from the following description and drawings.

According to at least one embodiment, a method of manufacturing an optoelectronic semiconductor chip, in particular:

A) forming a semiconductor layer sequence comprising at least one doped functional layer, wherein the functional layer comprises a binding complex containing at least one dopant and at least one co-dopant, wherein Selected one of the dopant and the codopant is an electron acceptor and the other is an electron donor,

B) activating the dopant by disrupting the bond complex using energy input, wherein the codopant comprises at least a portion remaining in the semiconductor layer sequence and at least some not forming a bond complex with the dopant. .

According to at least one other embodiment, the optoelectronic semiconductor chip comprises in particular an optoelectronic semiconductor chip with at least one doped functional layer, said functional layer containing a dopant and a codopant, wherein the semiconductor layer sequence is a lattice structure A semiconductor material, wherein one selected from the dopant and the codopant is an electron acceptor and the other is an electron donor, the codopant is bonded to the semiconductor material and / or disposed between the lattice points and the codopant is at least partially As such, it does not form a binding complex with the dopant.

The embodiments, features, and combinations of features described below are equally relevant to the optoelectronic semiconductor chip and the method for manufacturing the optoelectronic semiconductor chip unless explicitly stated otherwise.

The fact that one layer or one member is disposed or stacked on the "top" or "top" of another layer or another member, here and hereinafter, the one layer or one member on the other layer or another member It may mean that they are placed directly in direct mechanical and / or electrical contact. It may also mean that the one layer or one member is indirectly disposed on or on the other layer or another member. At this time, additional layers and / or members may be disposed between the one layer and the other layer or between the one member and the other member.

The fact that one layer or one member is disposed “between” two other layers or members is herein and hereinafter that the one layer or one member is directly in contact with one of the two other layers or members. By mechanical and / or electrical contact or indirect contact, and by direct mechanical and / or electrical contact or indirect contact with the other of the two other layers or members. Can be. Here, in indirect contact, additional layers and / or members are between the one layer and at least one of the two other layers or between the one member and at least one of the two other members. It may be disposed in.

As used herein, the concept of “doped functional layer” always means a layer containing dopants and co-dopants in the meaning described above.

By means of energy input according to the purpose in method step (B), the binding complex can be adjusted in the doped functional layer such that the compensating effect of the codopant on the doping properties of the intrinsic dopant can be offset. The doped functional layer is present, for example, in the form of an atomic bond between the dopant and the codopant of the doped functional layer or in the form of a bond complex between the dopant, the codopant and the semiconductor material. Compared with the conventional method, using the method described herein, according to suitable process conditions, direct reforming of the broken bond or bond complex can be prevented. In particular, the codopant may be bonded or accumulated between the lattice at other locations, ie not at the dopant side, within the crystal lattice of the semiconductor material of the doped functional layer or within the crystal lattice of the semiconductor material of another layer of the semiconductor layer sequence. In this position, the co-dopant can no longer compensate for the dopant. This increases the number of free charge carriers inserted by the dopant, i.e., uncompensated charge carriers, so that the codopant does not have to be released from the doped functional layer or semiconductor layer sequence. As the thus achievable conductivity is higher, the drive voltage of the optoelectronic semiconductor chip thus activated is also reduced.

The fact that the codopant does not at least partially form a binding complex with the dopant is here and hereinafter, in particular, at least a portion of the codopant is present in the doped functional layer, which portion does not form a binding complex with a portion of the dopant. As such, it may mean that portions of the dopant may contribute to an increase in free charge carrier density in the doped functional layer. The concept of "free charge carrier" then includes points in the p-type doped layer that are particularly deficient in holes, ie electrons, and which make a decisive contribution to the electrical conductivity of the p-type semiconductor, including electrons in the n-type doped layer. .

In particular, the optoelectronic semiconductor chip may be manufactured or formed as a light emitting diode (LED) or a laser diode and may comprise at least one active layer having an active region suitable for emitting electromagnetic radiation. Here and hereinafter, "light" or "electromagnetic radiation" may have the same meaning as electromagnetic radiation having at least one wavelength or wavelength region, in particular from the infrared wavelength region to the ultraviolet wavelength region of 200 nm or more to 20000 nm or less. . In this case, the light or electromagnetic radiation may include a visible wavelength region, that is, a near infrared to blue wavelength region, having one or more wavelengths between about 350 nm and about 1000 nm.

The semiconductor chip may include, for example, a pn junction, a double heterostructure, a single quantum well structure (SQW structure) or a multi quantum well structure (MQW structure) as an active region in the active layer. The term quantum well structure includes all structures within the scope of the present application that in particular charge carriers may experience quantization of energy states by "confinement". In particular, the term quantum well structure does not contain information about the dimensionality of quantization. The name includes in particular quantum boxes, quantum lines, quantum dots and each combination of these structures. The semiconductor layer sequence may comprise other functional layers and functional regions in addition to the active layer having the active region, which is p- and n-type doped charge carrier transport layers, ie electron- and hole transport layers, p-, n And undoped bondage-, cladding- and waveguide layers, barrier layers, planarization layers, buffer layers, protective layers, electrodes and a combination of the mentioned layers. The electrode may comprise one or more metal layers each containing Ag, Au, Sn, Ti, Pt, Pd, Cr, Al and / or Ni and / or zinc oxide, tin oxide, cadmium oxide, titanium oxide, indium oxide or indium tin, respectively. It may include one or more layers containing a transparent conductive oxide, such as oxide (ITO). In addition, additional layers such as buffer layers, barrier layers and / or protective layers can also be arranged perpendicular to the direction of the arrangement of the semiconductor layer sequence, for example around the semiconductor layer sequence, ie the sides of the semiconductor layer sequence. Can be placed in.

The semiconductor layer sequence or semiconductor chip may be formed or formed of an epitaxy layer sequence, ie, an epitaxially grown semiconductor layer sequence. At this time, the semiconductor chip or the semiconductor layer sequence may in particular be formed as or be a nitride semiconductor based. The concept of nitride semiconductors includes all nitride compound semiconductor materials. In this case, the semiconductor structure may include a bicomponent, tricomponent and / or quaternary compound of elements of the III main group and nitride. Examples of such materials are BN, AlGaN, GaN, InAlGaN or other III-V compounds. In this regard, the semiconductor layer sequence or semiconductor chip may be formed of InAlGaN based. In the InAlGaN-based semiconductor chip and semiconductor layer sequence, in particular, the epitaxially fabricated semiconductor layer sequence generally comprises one layer sequence consisting of different individual layers, and at least one individual layer included in the layer sequence The semiconductor chip and the semiconductor layer sequence in the case of containing a material of In _x Al _y Ga _1-xy N which is a III-V compound semiconductor material system belong. At this time, 0≤x≤1, 0≤y≤1, and x + y≤1. Preferably, the semiconductor layer sequence comprising at least one InGaAlN-based active layer can emit electromagnetic radiation, for example from the ultraviolet wavelength region to the green or green yellow wavelength region.

In addition, the semiconductor layer sequence may be formed of AlGaAs. In the AlGaAs-based semiconductor chip and the semiconductor layer sequence, in particular, the epitaxially produced semiconductor layer sequence generally comprises a layer sequence consisting of different layers, and the at least one individual layer included in the layer sequence is III-. The semiconductor chip and the semiconductor layer sequence in the case of containing a material of Al _x Ga _1-x As which is a V compound semiconductor material system belong. At this time, 0≤x≤1. In particular, the active layer comprising AlGaAs-based material may be suitable for emitting electromagnetic radiation including one or more spectral components in the red to infrared wavelength range. Such materials may also include In and / or P alternatively or additionally to the listed elements.

Alternatively or additionally, the semiconductor layer sequence may be InGaAlP based, that is, the semiconductor layer sequence may include individual layers that are different from each other, and at least one individual layer of the individual layers is In-III, which is a III-V compound semiconductor material system. _x Al _y Ga _{1 -x- y} P. At this time, 0≤x≤1, 0≤y≤1, and x + y≤1. For example, preferably, a semiconductor layer sequence or semiconductor chip comprising at least one InGaAlP-based active layer can emit electromagnetic radiation including one or more spectral components in the green to red wavelength region, for example.

Alternatively or additionally, the semiconductor layer sequence or semiconductor chip may also include II-VI compound semiconductor material systems in addition to or instead of III-V compound semiconductor materials. The II-VI compound semiconductor material is at least one element of the second main group or the second group such as, for example, Be, Mg, Ca, Sr, Cd, Zn, Sn, and, for example, O, S, Se, Te It may contain elements of the same sixth main group. In particular, the II-VI compound semiconductor material comprises a bicomponent, tricomponent or quaternary compound, the compound comprising at least one element of the second main group or the second group and at least one element of the sixth main group. Such bicomponent, tricomponent or quaternary compounds may include, for example, one or more dopants and additional components. For example, II / VI compound semiconductor materials include ZnO, ZnMgO, CdS, ZnCdS, MgBeO.

All of the materials described above do not necessarily have to contain mathematically correct compositions in accordance with the formulas provided. Rather, additional components and one or more dopants may be included that do not substantially alter the physical properties of the material. However, only the key components of the crystal lattice are simple to include in the formulas provided above, although they may be partially replaced by other minor components.

The semiconductor layer sequence may further include a substrate on which the above-described III-V or II-VI compound semiconductor material system is deposited. The substrate may, for example, comprise a semiconductor material having a compound semiconductor material system as listed above. For example, the substrate may comprise or consist of GaP, GaN, SiC, Si and / or Ge or sapphire. The substrate may be formed as a growth substrate, which means that the semiconductor layer sequence is epitaxially grown on the substrate and the functional layer spaced farthest from the substrate in the semiconductor layer sequence is the top layer in the growth direction. Alternatively, the substrate may be formed as a carrier substrate, on which the semiconductor layer sequence first grown on the growth substrate is transferred, for example by rebonding, on top of the growth substrate in the growth direction. The layers of the located semiconductor layer sequence are transferred in a manner that is located closest to the carrier substrate after rebonding. The growth substrate may be partially or completely removed after the transfer step, so that a layer of semiconductor layer sequence grown on the growth substrate may first be exposed. In particular, the optoelectronic semiconductor chip including the carrier substrate may be formed as or be a thin film semiconductor chip.

The thin film semiconductor chip is particularly characterized by at least one of the following characteristic characteristics:

 A reflective layer is laminated or formed on the first major surface facing the carrier in the radiation generating epitaxy layer sequence, the reflective layer retroreflecting at least a portion of the electromagnetic radiation generated in the epitaxy layer sequence to the layer sequence;

The thickness of the epitaxy layer sequence is in the range of up to 20 μm, in particular in the range of 10 μm; And

The epitaxy layer sequence comprises at least one semiconductor layer with at least one side with a mixed structure, which, in an ideal case, leads the light to be nearly ergodic distributed in the epitaxy layer sequence, i.e. Includes an ergodic stochastic variance behavior.

The basic principle of a thin film light emitting diode chip is described, for example, in I. Schnitzer et al., Appl. Phys. Lett. 63 (6), October 18, 1993, 2174-2176, the disclosure content of which is hereby incorporated by reference only.

In the method step (A), for example, the doped functional layer can be provided in the form of a separate layer or in the form of a doped functional layer stack as a semiconductor layer sequence. In addition, the semiconductor layer sequence may be provided as or may be formed as some completed part of a semiconductor chip. This includes, for example, a semiconductor layer sequence comprising a substrate, such as a growth substrate, wherein a plurality of functional layers are grown, including a doped functional layer containing dopants and codopants on the substrate, wherein the dopant and codopant It may mean that the doped functional layer containing is grown as a layer located on the top when viewed in the growth direction. Alternatively, the substrate may be a carrier substrate to which a semiconductor layer sequence including the doped functional layer is transferred, and then the growth substrate is removed to expose the doped functional layer.

In addition, the semiconductor layer sequence may be formed comprising a plurality of functional layers in method step A, wherein a doped functional layer containing a dopant and a codopant is disposed between two other functional layers, The functional layer is formed such that it is not the topmost layer in the semiconductor layer sequence. One or more other functional layers are respectively arranged above and below the doped functional layer in the growth direction, wherein at least the layers directly adjacent to the doped functional layer are different from the doped functional layer, in particular if differently doped here and below Wherein the doped functional layer can be referred to as a so-called "buried" layer.

In particular, the semiconductor chip can already be completed in method step A, which means that the semiconductor layer sequence already contains the functional layers of all the semiconductor layer sequences necessary for driving the semiconductor chip after the method step A. do. The semiconductor layer sequence can be formed, for example, in a wafer combination. The semiconductor layer sequence thus completed may be formed and provided in a wafer combination, or as already individual semiconductor chips individually correspondingly after the implementation of method step A).

The semiconductor chip or semiconductor layer sequence may comprise an active region, for example, between a p-type doped layer and an n-type doped layer disposed thereafter in the growth direction, such that the polarization in the growth direction is p-type. The doped region is reversed compared to the conventional semiconductor chip located behind the n-type doped region in the growth direction. Depending on the formation of the semiconductor chip including the growth substrate or the carrier substrate, the n-type doped layer or p-type doped layer may be formed as a buried doped functional layer.

The buried and doped functional layer includes at least one n-type doped ("n-type") tunnel junction layer and at least one p-type doped ("p-type") tunnel junction layer, for example in an optoelectronic semiconductor chip. It can be formed with one tunnel junction. The at least one doped functional layer containing the dopant and the codopant may be formed of at least one n-type doped tunnel junction layer or at least one p-type doped tunnel junction layer. After the tunnel junction, an active layer having an active region in a direction away from the substrate in the semiconductor layer sequence may be disposed. In this case, an undoped region may be disposed between the at least one n-type tunnel junction layer and the at least one p-type tunnel junction layer, and the undoped region may be formed of at least one intermediate layer that is not doped. The type tunnel junction layer and the p-type tunnel junction layer are not directly in contact with each other and are separated from each other by at least one undoped intermediate layer. The concept of "tunnel junction layer" is used to distinguish the semiconductor layer sequence or the remaining functional layers of the semiconductor chip, which means that an n-type tunnel junction layer or a p-type tunnel junction layer, which is called as such, is disposed at the tunnel junction.

By separating the n-type tunnel junction layer and the p-type tunnel junction layer from each other by an undoped region, a negative effect that different charge carriers are compensated at the interface is prevented, otherwise, the p-type tunnel junction layer and the n-type tunnel junction layer are prevented. When the layers are in direct contact, charge carriers can diffuse beyond the interface. The undoped region is inserted between the n-type tunnel junction layer and the p-type tunnel junction layer, thereby creating a region with a low charge carrier density in the tunnel junction, but being undoped in the form of one or more undoped intermediate layers. Regions have a negative effect on the electrical properties of tunnel junctions, in particular compared to regions where charge carriers are bilaterally compensated by diffusion across the interface at the interface between the n-type tunnel junction layer and the directly adjacent p-type tunnel junction layer. The negative effect on the forward voltage can be lessened.

In addition, the semiconductor layer sequence or semiconductor chip may be formed as a stacked LED having a plurality of stacked and grown active layers, wherein each active layer is provided between at least one n-type doped layer and a p-type doped layer each time. It is also arranged in combination with, for example, the tunnel junction layer. As such, the semiconductor layer sequence formed as a stacked LED may include at least one buried doped functional layer.

Structures having the form of normal polarization or reverse polarization, tunnel junction layers, and stacked active regions, described above for semiconductor layer sequences or semiconductor chips, are known to those skilled in the art and are not described herein any further. In all such structures, the structure may comprise buried doped functional layers, which may include dopants and codopants, adjacent to layers that may serve as a diffusion barrier for the codopant. It is common. In such buried doped functional layers, conventional dopant activation may be nearly impossible or not at all possible, for example, using the conventional RTP method described above.

The dopant for the p-type doped functional layer, ie at least one suitable electron acceptor, cannot be inserted in pure form into the semiconductor material of the doped functional layer, generally at least when the doping intensity to be reached is high. Instead, the dopant is present in complex with at least one other material, ie as a codopant. The other material often serves as an electron donor for the semiconductor material, which compensates the electron acceptor material, ie the dopant, in terms of electrical effects. In particular, the doped functional layer may be a p-type doped layer in which the dopant comprises or is an electron acceptor material, while the co-dopant comprises an electron donor material or is an electron donor material. The activation step according to method step (B) is suitable for continually creating an electrical effect of at least a portion of the dopant in the semiconductor material, ie for increasing the p-type conductivity.

More preferably, the dopant comprises or is magnesium for the p-type doped functional layer in a bandwidth semiconductor system, such as for example a nitride compound semiconductor system. Magnesium is generally incorporated into semiconductor materials in complex with hydrogen as a codopant. The activation step according to method step (B) produces an electrical effect of at least a portion of magnesium as a p-type dopant. This effect is compensated for by hydrogen. In II-VI compound semiconductor systems such as ZnSe, for example, the dopant contains or is nitrogen. Preferably here, the codopant may be hydrogen.

Alternatively, the doped functional layer may be an n-type doped layer, ie the dopant is an electron donor material, while the codopant is an electron acceptor material. This may be well suited, for example, for semiconductor materials with relatively low bandgap, such as CdTe or GaAs based compound semiconductor materials.

Since the method described herein does not require the release of the codopant, it is particularly suitable for doped functional layers where the codopant cannot diffuse out for fundamental reasons, for example, where the doped functional layer is This is because it is a buried layer in the sense of. Therefore, the method described herein may initially offer the possibility to activate these layers. This type of activation is essential for PILS ("polarity inverted LED structures") and stacked LEDs as described above, in which case the p-type doped functional layer comprises Mg as dopant and hydrogen as co-dopant, for example. This is because it cannot be activated by the RTP-based temperature control step for the purpose of only release of the codopant. The stacked LEDs are based, for example, on GaN-based or other of the compound semiconductor materials listed above. The temperature control step targets only the release of the codopant.

Energy supply and input is needed to destroy the bonds of the codopant that passivates the dopant for the dopant or crystal atom, as intended and as permanently as possible. At this time, energy in the method step (B) can be input by current generation in the doped functional layer. This may be referred to here and hereinafter as "electrical activation." In electrical activation, at least the doped functional layer can be electrically connected to an external current source. In addition, the optoelectronic semiconductor chip already completed and formed in connection with the semiconductor layer sequence, for example in method step A, may be electrically operated for a certain time, ie connected to an external current source and a voltage source. The optoelectronic semiconductor chip can be in a wafer combination such that a plurality of optoelectronic semiconductor chips or semiconductor layer sequences can be activated simultaneously. Alternatively to this, the semiconductor chip can already be individualized in the method step (A) and thereby separated from the wafer assembly, so that the semiconductor chip can be activated individually and independently of the other semiconductor chips of the wafer combination. With regard to the required current densities described below, the electrical activation of an individualized semiconductor layer sequence or an individualized optoelectronic semiconductor chip may be advantageous, since dimensional determination of this method may only be technically limited in larger wafer disks. to be.

Alternatively, the current can be generated by induction with an external suitable coil device without contact. At this time, in a plane parallel to the extended surface of the doped functional layer, a circular current or a plurality of original currents are grown in the semiconductor layer sequence at least in the doped functional layer or additionally in other layers of the semiconductor layer sequence. And perpendicular to the direction and thereby perpendicular to the driving conditional current direction of the semiconductor chip.

If the semiconductor layer sequence is formed on an electrically insulating sapphire substrate, for example, as a growth substrate in the method step (A), electrical activation by electrical connection occurs after the semiconductor layer sequence is rebonded onto the electrically conductive carrier substrate and the growth substrate is removed. Can be started. Alternatively or in addition to this, in some cases, electrical activation may already be effected by induction before the rebonding step, which is no longer necessary.

In the case of electrical activation by electrical connection and induction, one can observe that the required drive voltage continues to decrease to a minimum value, which is kept permanent. At this time, the generated current density may be 50 A / cm 2, wherein higher current density may accelerate the activation.

Further, more preferably, additionally, thermal energy can be supplied for current generation, so that the temperature of the semiconductor layer sequence or the temperature of the optoelectronic semiconductor chip, at least the temperature of the doped functional layer, is increased. The temperature of the doped functional layer may be at least about 80 ° C and more preferably at least 100 ° C. In addition, the current density generated at such a temperature may be 10 A / cm 2 or more. Compared with known activation methods, the temperature for the activation methods described herein can be up to 400 ° C. and also up to 300 ° C. At higher temperatures, activation can be accelerated almost exponentially, while at the same time the required current density can be lower. The measurement confirmed that saturation may already occur in the reduction of the drive voltage at about 300 ° C., for example after about 1 minute. The activation time should be very accurate, i.e. it should not be chosen particularly long, otherwise an additional reduction in light emission may be manifested by the aging of the semiconductor layer sequence. Of course, in the parameter range provided, the aging starts significantly later and proceeds more slowly than when saturation is at the level reduced drive voltage. In particular, the activation time may take up to 10 minutes, more preferably up to 5 minutes, in addition to the electrical activation, as well as in the alternative and additional activation processes described below.

Thermal energy can be supplied by an external heat source, ie by heating. Alternatively or additionally, the thermal energy can also be supplied by a current which is itself generated by ohmic losses. The effect of the temperature increase caused by the input thermal energy is that, together with the generated current flow, the coder punt, ie, the aforementioned hydrogen, can be shifted so that the inherent dopant, ie the aforementioned magnesium, is activated.

Alternatively or additionally to the generation of current and / or input of thermal energy, in step B, energy can be input while electromagnetic radiation is irradiated. This point may also be referred to herein as " electromagnetic activation ". Electromagnetic activation is such that the semiconductor layer sequence formed in method step (A) is irradiated with electromagnetic radiation, the electromagnetic radiation being resonant or non-resonant with the absorption wavelength or absorption band of the doped functional layer and / or another layer of the semiconductor layer sequence. Can mean resonating.

By irradiating electromagnetic radiation, additional charge carriers can be generated, for example, which can cause a larger current to be induced in connection with the aforementioned electrical activation. In particular, this may be advantageous, for example, even when there are essentially very few free charge carriers or no free charge carriers present in the doped functional layer. Also, in the case of resonance irradiation, the charge carriers can be excited according to the purpose in the layers from which activation will begin, ie the doped functional layer. In addition, activation of the doped functional layer can only be achieved by electromagnetic activation.

At this time, the frequency of the irradiated electromagnetic radiation determines the electromagnetic activation method. Activation in conventional semiconductor materials is generally non-resonant using microwave radiation, ie electromagnetic radiation having a wavelength of about 1 millimeter or greater and less than about 1 meter or a frequency of about 300 MHz to about 300 GHz. The energy transfer to the atomic bond can then be achieved in particular by excitation of rotons and / or phonons. The phonon may typically have an excitation energy of a few 10 meV in the doped functional layer, and the rotone may typically have an excitation energy ranging from less than 1 meV to several meV. Rotons can include the intrinsic rotation of atoms as well as the intrinsic rotation of complexes such as excitons. The use of so-called terahertz radiation, ie at least about 100 micrometers and electromagnetic radiation having a wavelength of about 1 millimeter or less, or a frequency of about 300 GHz to about 3 THz, generally refers to resonance activation in common semiconductor materials, the resonance activation The lattice vibrations, ie phonons, can be produced directly.

Process conditions such as frequency, power, atmosphere, time, and additional susceptors capable of absorbing electromagnetic radiation define the extent and success of electromagnetic activation. In particular, electromagnetic activation can be carried out using a mixture of resonance activation and non-resonance activation. For example, when the output is 100 to 4000 watts, the frequency of the electromagnetic radiation irradiated for the buried doped functional layer of p-GaN material may be between 5 and 10 GHz. Preferably, the irradiation process may be carried out over a time ranging from 10 seconds to 1 hour. The frequency can also be changed to prevent so-called "hot spots" and so-called "arcing", ie local overheating and flashover. Additionally or alternatively, the semiconductor layer sequence can be rotated and / or rotated and translated relative to or against the device for the irradiation of electromagnetic radiation.

Activation with electromagnetic radiation has the additional advantage that it can be used at any time in the chip cycle. In conventional thermal activation, the activation step is always one of the first process steps within the chip cycle range, as this typically requires a very high temperature, for example above 700 ° C, as described above. ; This high temperature generally damages many "following components" or "following layers" that are gradually deposited on the semiconductor layer sequence within the method step (A) of the chip cycle. In contrast, if electromagnetic radiation is coupled to the material used, for example a p-GaN material doped functional layer, as desired, this process step can be incorporated into the process cycle at a later point in time. The wavelength characteristic is that the dopant-codopant- or dopant-codopant semiconductor crystal, ie activating here and almost only, where, for example, the electromagnetic radiation is "used" exactly, with the activation energy fairly selective. Because it can be adjusted to couple in the binding complex. This gives more design freedom and greater freedom in the so-called chip flow, for example with regard to the possible ordering of the individual fixtures. In addition, the activation efficiency can be increased, for example, at the time when activation is carried out after mesa etching, i.e. at the point where the crystal plane exposed by the generated flat part is larger and thus the co- dopant can be discharged better. May be increased by implementation.

The semiconductor layer sequence or the optoelectronic semiconductor chip formed in the method step (A) may comprise a plurality, i.e., at least two, doped functional layers or a plurality of doped functional layers disposed in direct contact with each other. Another functional layer is arranged in between. Activation of the plurality of doped functional layers may occur simultaneously in method step (B). Alternatively to this, each of the doped functional layers can be activated in a method step (B) each adapted for activation in connection with the aforementioned parameters.

Proof of change in the local binding state of the codopant can be carried out or performed in various ways. A very sensitive method is spin resonance as described, for example, in Zvanut et al., APL 95, 1884 (2004), the disclosure content of which is incorporated by reference in this regard. The result of altered binding of the codopant is the remarkable altered g-factor of the charge carriers around the bond, where the g factor is called the gyro magnetic factor or the so-called lande factor. The altered g factor appears at the altered resonance frequency.

In addition, the binding state of the codopant can be demonstrated directly by the characteristic vibrational frequency of the binding state in the crystal lattice. Thus, for example, Mg-H and NH bonds in GaN include vibration modes with energies of 2000 and 4000 waves, depending on the position and bonding state in the crystal lattice, using Raman spectroscopy and infrared (Fourier) spectroscopy. And Neugebauer and van de Walle, PRL 75, 4452 (1995), Van de Walle, Phys. Rev. B 56, 10020 (1997), Kaschner et al., APL 74, 328 (1999), Harima et al., APL 75, 1383, (1999) and Cusco et al., APL 84, 897 (2004). The disclosures of these documents are incorporated by reference in this regard.

Hereinafter, other advantages, advantageous embodiments and developments of the present invention are derived from the embodiments described with reference to FIGS. 1A to 5.

1A-1D are schematic diagrams of method steps of a method of manufacturing an optoelectronic semiconductor chip according to various embodiments.
2-4 are schematic diagrams of method steps of a method of manufacturing an optoelectronic semiconductor chip according to another embodiment.
5 is a driving voltage measurement graph according to an activation time.

In the embodiments and the drawings, the components having the same or the same effects may have the same reference numerals. The depicted elements and size ratios between the elements are not basically seen on an accurate scale, but rather individual elements such as layers, components, elements, regions, for example, are exaggerated and thick for better expression and / or better understanding. It may be shown in large dimensions.

1A-1D show various embodiments of method step (A) for a method of manufacturing an optoelectronic semiconductor chip. 1A to 1D, a semiconductor layer sequence 100, 200, 300 or 400 is formed, respectively, which layer sequence comprises at least one substrate 1, a doped functional layer 7 and an active region ( 8) and other functional layers 9. For electrical contact, the side of the substrate 1 facing away from the doped functional layer 7 and the surface of each semiconductor layer sequence 100, 200, 300, 400 facing away from the substrate 1. The electrode layers 10, 11 are stacked, and the electrode layers may comprise one or more metals and / or one or more transparent conductive oxides as described in the general description. The semiconductor layer sequence of the illustrated embodiment is formed as a nitride compound semiconductor layer sequence in a purely illustrative sense. Alternatively or in addition thereto, the semiconductor layer sequence may also include other compound semiconductor materials described in the general description.

Further, hereinafter, purely illustratively already completed semiconductor layer sequences 100, 200, 300, 400 with respect to the semiconductor chips to be manufactured, that is, corresponding to semiconductor chips already completed with respect to each layer structure A semiconductor layer sequence is formed. Alternatively to this, also a partially completed semiconductor layer sequence may be formed in method step A, which layer comprises at least the doped functional layer 7. In addition, the semiconductor layer sequence can be formed and provided in the wafer combination yet in method step (A) but before the individualization step to be carried out later.

The following description is purely illustrative and limited to the doped functional layer 7, ie the p-type doped layer and other functional layers. The other functional layers are suitably formed of n-type or p-type. Alternatively, the polarization of the doped functional layer 7 and other functional layers, or the polarization of the dopant and optionally the codopant, may be reversed, ie the doped functional layer 7 is formed by n-type doping. do.

The substrate 1 of the semiconductor layer sequence 100 according to the embodiment of FIG. 1A is a growth substrate, on which the layers 7, 8, 9 located thereon are epitaxy within the scope of the method step A. FIG. Earl is grown. In FIG. 1A, the growth direction is indicated using the arrow 99 as in FIGS. 1B to 1D below.

In this embodiment, preferably the n-type substrate serves as a growth substrate. Possible n-type substrates are, for example, n-GaN, n-SiC, n-Si (111). However, an electrically nonconductive substrate may also be used, for example sapphire, with the electrode layer 10 disposed on the side of the substrate 1 facing the layers 7, 8, 9.

The functional layer 9 is an n-type layer and is formed as a gallium nitride layer doped with silicon in the illustrated embodiment. An active layer 8 is grown on top of the functional layer 9, the active layer comprising a single quantum well structure or a multi quantum well structure provided for radiation generation as the active region. Preferably, the active layer 8 is based on In _y Ga _1-y N, which is a III-V semiconductor material system, comprising alternating optically active layers and barrier layers, where 0 ≦ y ≦ 1. Preferably, the active layer 8 is suitable for generating electromagnetic radiation in the spectral region of ultraviolet, blue, blue green, yellow or red, wherein the wavelength of the emitted electromagnetic radiation is determined using the composition and structure of the active layer 8. Can be adjusted. Preferably, the indium concentration in the active layer is between 10 and 60%.

A doped functional layer 7 is epitaxially grown on the active layer 8, and the doped functional layer not only contains GaN or AlGaN as a semiconductor material, but also magnesium as a dopant for p-type doping, It contains hydrogen, for example, to counteract the degradation of the crystal quality of the semiconductor material as intrinsic defects are inserted by the insertion of dopants during crystal growth. The dopant and codopant form a bond complex such that the free charge carriers inherently produced by the dopant are compensated and the electrical neutrality of the semiconductor crystal is at least partially reformed.

The structure of the semiconductor layer sequence 100 is the arrangement of the n-type functional layer 9 between the substrate 1 and the active layer 8, and the p-type doped functional layer formed on the active layer 8 in the growth direction 99. Corresponding to the arrangement of (7) of conventional light emitting diodes (LEDs), it may further comprise other functional layers such as buffer layers, barrier layers and / or diffusion barrier layers, which other functional layers may for reasons of overview Not shown.

In FIG. 1B, the semiconductor layer sequence 200 according to another embodiment has a reverse polarization compared to the semiconductor layer sequence 100, wherein the p-type doped functional layer 7 is formed between the growth substrate 1 and the active layer 8. Is formed, and another functional layer 9 doped n-type is formed on the active layer 8 in the growth direction 99. The layer composition of each of the layers 7, 8, 9 corresponds to the previous embodiment.

In addition, the semiconductor layer sequence 200 is formed of another n-type functional layer of silicon-doped GaN material between the substrate 1 formed as the n-type growth substrate and the p-type doped functional layer 7 as in the previous embodiment. It includes 2). a highly doped n-type tunnel junction layer 4, a diffusion barrier layer 5 and between these functional layers for effective electrical connection of the p-type doped functional layer 7 to the other n-type functional layer 2. A tunnel junction 3 is formed with a highly doped p-type tunnel junction layer 6. The tunnel junction 3 is formed as described in the general description, where the p-type tunnel junction layer 6, like the p-type doped functional layer 7, contains magnesium as dopant and hydrogen as co-dopant. . Thus, the highly doped p-type tunnel junction layer 6, like the doped functional layer 7, is formed as a doped functional layer to be activated in light of the present description.

Unlike the semiconductor layer sequence 100 of the embodiment according to FIG. 1A, the functional layers 6, 7 doped in the semiconductor layer sequence 200 are formed as so-called buried doped functional layers, the functional layer being another functional semiconductor. Disposed between the layers. Activation of layers 6, 7 by known activation methods using release of codopant is not possible for semiconductor layer sequence 200.

The semiconductor layer sequence 200 may comprise other functional layers (not shown, for example, a buffer layer between the substrate 1 and the functional layer 2 and / or a diffusion barrier layer between the doped functional layer 7 and the active layer 8). ) May be included.

1C shows a semiconductor layer sequence 300 formed as a thin film semiconductor chip, which likewise includes a doped functional layer 7 embedded therein. The layers 7, 8, 9 correspond to the layers 7, 8, 9 of FIG. 1A, wherein after growth the layers, for example located on a growth substrate of sapphire material, are re-bonded using a carrier substrate ( 1), and thus the growth direction 99 indicates the direction of the carrier substrate 1. The growth substrate was removed after rebonding. The semiconductor layer sequence 300 may include and / or include other functional layers, such as, for example, a reflective layer between the carrier substrate 1 and the p-type doped functional layer 7, and the thin film described in the general description. It may have other characteristics of the semiconductor chip. By rebonding, the doped functional layer 7 is likewise present as a buried layer, which can not be activated after rebonding using a known activation method based on the release of the codopant. In the known activation method, the activation should preferably be carried out at a point prior to rebonding, at which point the doped functional layer 7 is still exposed.

Alternatives to the manner of forming as a thin film semiconductor chip on a carrier substrate, layers comprising a functional layer 7 doped between the substrate 1 and the active layer 8 also by epitaxial growth on a p-type growth substrate. A layer sequence of (7, 8, 9) can be formed. In this case, the p-type substrate may be formed of p-GaN, p-SiC or p-Si 111, for example, where the growth direction 99 will be oriented away from the substrate 1.

FIG. 1D shows a semiconductor layer sequence 400 including an inverse structure according to FIG. 1B, which is also formed as a stacked structure including another active layer 8 ′. The doped functional layer 7 ′ corresponds to the doped functional layer 7.

The other functional layers 3 ', 9' correspond to the layers 3, 9, in which the tunnel junction 3 ', like the tunnel junction 3, is the tunnel junction layer 4, described in connection with FIG. 6) and diffusion barrier layer 5 (not shown).

In the activation method in the subsequent method step (B), described in accordance with the preceding general description and the embodiments below, the timing at which activation according to the method step (B) is carried out in the manufacturing process is carried out for each semiconductor layer sequence. It is independent of the formation and manufacturing process. Purely illustrative, an embodiment for method step (B) is described based on semiconductor layer sequence 200 according to FIG. 1B.

In method step B according to the embodiment of FIG. 2, the doped functional layer 7 and the highly doped p-type tunnel junction layer 6 are activated as energy is input. To this end, the semiconductor layer sequence 200 is connected to an external current supply and voltage supply 12. At this time, in the illustrated embodiment, the current density in the semiconductor layer sequence 200 or in particular the doped functional layer 7 and the highly doped p-type tunnel junction layer 6 is produced at about 50 A / cm 2. In addition, the semiconductor layer sequence 200 is brought to a temperature higher than the general ambient temperature and the driving temperature by the supply of the thermal energy 13. In the illustrated embodiment, the semiconductor layer sequence 200 is heated to a temperature of at least 80 ° C. by external heating (not shown). At least a portion of the supplied thermal energy may be generated by ohmic loss of injected current.

Experimentally, when driving the semiconductor layer sequence 200 by the current supply unit and the voltage supply unit 12 under the aforementioned conditions, the required driving voltage continuously decreases with time, reaches the saturation value, and the saturation value. Was confirmed to be permanent. This means that the current-voltage characteristic of the semiconductor layer sequence can be improved by the method step (B) and can be maintained permanently after the method step (B). FIG. 5 shows a measurement of the driving voltage U (magnetic unit) to be applied at a specific driving current according to the activation time t of magnetic activation (magnetic unit). It has also been found that an increase in current density and / or an increase in temperature can cause an acceleration of voltage reduction and an acceleration of saturation attainment.

By the above-mentioned activation drive of the semiconductor layer sequence 200, the dopant-codopant- and dopant-codopant semiconductor crystal-bond complexes can be destroyed in layers 6 and 7. The complex is formed in the manufacture of the semiconductor layer sequence 200 in method step (A). In addition to the conventional activation methods, at least a portion of the codopant may be bonded to the semiconductor crystals of the layers 6 and 7 or accumulated between the lattice, rather than in a way to form a bond complex at another location, ie in the dopant. have. In this way, in the case of the electrical activation described herein, it is not necessary to at least partially export the codopant from the semiconductor layer sequence as is necessary in the known pure thermal activation method.

By virtue of the advantageous current densities mentioned above for method step (B), the electrical activation shown uses at least one buried doped functional layer 7 using current injection by an external current supply and voltage supply 12. It is well suited for semiconductor layers sequences that are already individualized, and conventional activation methods in these layers sequences are technically virtually impossible or not at all. In addition, the case where the method step (B) shown herein is applied to the semiconductor layer sequence in the wafer combination is never excluded.

In particular, the method step (B) according to the embodiment of FIG. 3 is suitable for the semiconductor layer sequence and the already individualized semiconductor layer sequence in the wafer combination. At this time, current is generated in the semiconductor layer sequence 200 or at least in the doped functional layer 7 and also in the highly doped p-type tunnel junction layer 6 to be activated by induction using the device 14, such energy Causes breakage of the binding complex containing dopant and codopant. In the illustrated embodiment, the induction device 14 is purely exemplary and implemented as a coil, where any device capable of causing sufficient induction current in the semiconductor layer sequence 200 may be suitable.

By means of the device 14, the source current is induced in the layers 6, 7 using free charge carriers, and the activation effect described above with respect to FIG. 2 can be achieved by the source current. The original current is perpendicular to the growth direction 99 and occurs parallel to the extending surface of the functional layers of the semiconductor layer sequence 200. Additionally, thermal energy may be further supplied to the semiconductor layer sequence 200 in the form of external heating (not shown) and further supplied by ohmic loss of the original current.

In addition, in the illustrated embodiment according to FIG. 3, the semiconductor layer sequence 200 is irradiated with electromagnetic radiation 15, which is resonant or non-resonant with the absorption wavelength of the functional layer and especially the layers 6, 7 to be activated. do. Irradiation of electromagnetic radiation 15 additionally creates free charge carriers, which can make the current strength of the induced source current stronger. This is very advantageous if there are essentially only some free charge carriers or no free charge carriers present after the method step A in the layers 6, 7 to be activated. In particular, in the case of resonance irradiation, further free charge carriers can be excited in the layers 6 and 7 to be activated as desired, so that the activation efficiency can be improved.

As shown in accordance with another embodiment for method step (B) in FIG. 4, activation, ie destruction of complexes containing dopants and codopants, can only be carried out when energy is supplied in the form of electromagnetic radiation 15. Can be. The frequency of the electromagnetic radiation 15 determines the activation scheme. With microwave radiation, electromagnetic activation is performed non-resonantly, and with terahertz radiation, resonance is electromagnetic resonance. Process conditions such as frequency, power, atmosphere, time and / or additional absorption centers for electromagnetic radiation 15 define the degree of activation and success. In the case of non-resonance, energy is transferred to the atomic bond, in particular by excitation of phonon and rotone. In the case of resonance, lattice vibrations, ie phonons, are produced directly, and phonons can destroy the binding complexes containing dopants and codopants.

The method step (B) according to FIGS. 3 and 4 may advantageously be used at any time within the fabrication process of the semiconductor chip or even after individualization in the range of chip cycles at the wafer level, wherein the method step is made contactless, and FIG. This is because, like the method step (B) according to the embodiment of 2, it does not require an exposed doped functional layer 7 to be activated. Therefore, more degrees of freedom are obtained with regard to the possible ordering of the individual processes in the design and so-called chipflow. In addition, activation efficiency can be increased, for example, by activation being performed after mesa etching so that the exposed semiconductor crystal surface is larger and at least a portion of the codopant can be discharged.

Embodiments of the method step (B) described herein and other embodiments according to the general description can be used in combination or in turn, for individual layers to be activated as well as for a plurality of layers to be activated in a semiconductor layer sequence. have.

If necessary, method step (B) can now be linked to another known method step for the completion of a semiconductor chip comprising an activated semiconductor layer sequence.

The present invention is not limited to this embodiment by the description based on the embodiment. Rather, the invention includes each new feature and each combination of features, which in particular is a feature in the claims, even if such feature or such combination is not explicitly presented in the claims or the embodiment itself. Cover each combination of these.

Claims (15)

In the manufacturing method of the optoelectronic semiconductor chip,
A) manufacturing a semiconductor layer sequence 200 comprising at least one doped functional layer 7 (the functional layer comprises a bonding complex containing at least one dopant and at least one codopant, wherein the dopant And one selected from said codopant is an electron acceptor and the other is an electron donor),
B) activating the dopant by disrupting the bond complex using energy input, wherein the codopant remains at least partially in the semiconductor layer sequence 200 and at least some does not form a bond complex with the dopant And a method of manufacturing an optoelectronic semiconductor chip. The method according to claim 1,
The semiconductor layer sequence 200 is formed in step A, wherein the doped functional layer 7 is formed so as to be disposed between two other functional layers 2, 8. Way. The method according to claim 1 or 2,
In the step A, the semiconductor layer sequence (200) is a method of manufacturing an optoelectronic semiconductor chip, characterized in that the individualized after being completed in the wafer assembly. The method according to any one of claims 1 to 3,
And the dopant comprises magnesium and the codopant comprises hydrogen. The method according to any one of claims 1 to 4,
In step B, the energy input is performed by generating current in the doped functional layer (7). The method according to claim 5,
And wherein said current is generated by induction without contact. The method according to claim 5,
And the current is generated by the at least doped functional layer (7) being electrically connected to an external current source (12). The method according to any one of claims 5 to 7,
Thermal energy (13) is additionally supplied to the current generation. The method according to claim 8,
The thermal energy (13) is at least partly supplied by a current. The method according to any one of claims 1 to 9,
The energy input in step B is carried out as the electromagnetic radiation (15) is irradiated. The method according to claim 10,
The electromagnetic radiation (15) resonates at least in part with the absorption wavelength of the doped functional layer (7). The method according to claim 10 or 11,
The method of manufacturing an optoelectronic semiconductor chip, characterized in that the electromagnetic radiation is not at least partially resonant with the absorption wavelength of the doped functional layer. An optoelectronic semiconductor chip comprising a semiconductor layer sequence 200 having at least one doped functional layer 7 containing at least one dopant and at least one codopant.
The semiconductor layer sequence 200 includes a semiconductor material having a lattice structure,
One selected from the dopant and the codopant is an electron acceptor and the other is an electron donor,
The codopant is bonded to the semiconductor material and / or disposed between lattice points, and
And wherein the codopant does not at least partially form a bond complex with the dopant. The method according to claim 13,
The doped functional layer (7) is characterized in that it is arranged between two different functional layers (3, 8). The method according to claim 13 or 14,
And the dopant comprises magnesium and the codopant comprises hydrogen.

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